An aircraft engine, for example a turbine engine, air is drawn into the front of the engine through an inlet, compressed by a compressor, and mixed with fuel in a combustor. The mixture is burned and passes through a turbine. The flow of combustion gas expands through the turbine which in turn spins the shaft and provides power to the compressor. The hot exhaust gases are further expanded through nozzles at the back of the engine, generating powerful thrust, which drives the aircraft forward.
A fan casing can define the inlet and a fan formed by a plurality of blades. Variable conditions exist in which an engine operates. Foreign objects, such as birds, hailstones, ice, sand, and rain may be entrained in the inlet of the engine where impact with portions of the engine can occur, including impact with an interior of the fan casing. In some cases impact may cause a portion of the blade to become torn out which is commonly known as fan blade out. The loose fan blade can impact the interior of the fan casing as well.
The fan casing can be formed in part by composite materials formed to withstand impacts caused by foreign objects or fan blade outs. Depending on the thickness and of the composite material in the fan casing, the composite material can add a significant amount of weight to the engine.